What is the key mechanical difference between optical image stabilization and sensor-shift stabilization inside the iPhone, and how does each improve a photo's sharpness?

Optical Image Stabilization, or OIS, inside the iPhone works by mechanically shifting specific lens elements within the camera module. When the iPhone experiences shake, internal gyroscopes and accelerometers detect the camera's movement. Tiny electromagnetic actuators then precisely move one or more lens elements in the direction opposite to the detected shake. This movement redirects the incoming light path, effectively keeping the image projected onto the camera's sensor stationary, even as the phone itself moves. This action prevents motion blur, which is the undesirable smearing of an image that occurs when light from a single point in the scene falls on different sensor pixels during the exposure time. Sensor-shift stabilization, in contrast, counteracts camera shake by physically moving the entire image sensor itself within the camera module. Similar to OIS, internal sensors detect camera movement. Instead of shifting lenses, miniature actuators rapidly and precisely move the image sensor in the direction opposite to the camera's shake. This means the sensor actively moves to remain aligned with the image projected by the lens, compensating for the phone's physical movement. The key mechanical difference between OIS and sensor-shift stabilization is that OIS moves lens elements to stabilize the light path, while sensor-shift stabilization moves the image sensor itself to stabilize the recording surface. Both OIS and sensor-shift stabilization improve a photo's sharpness by preventing motion blur caused by unintended camera movement during the exposure. By ensuring that light from a single point in the scene consistently hits the same pixel location on the sensor throughout the exposure, regardless of slight camera shakes, these technologies prevent the image from becoming smeared. This results in clearer, crisper photographs, especially beneficial in low-light conditions or when longer exposure times are required, where camera shake would otherwise significantly degrade image quality.